1. Field of Invention
The present invention relates to a liquid crystal display device, a manufacturing method therefor, and an electronic apparatus. Particularly, the present invention relates to a construction of a transflective liquid crystal display device with excellent visibility, which is capable of a sufficiently bright display in both a reflective mode and transmissive mode.
2. Description of Related Art
The related art includes a liquid display device to enable a display to be viewed in the light by using external light, like in a previous related art reflective liquid crystal display device, and to enable a display to be viewed in the dark by using an internal light source. The liquid crystal display device uses a display system for both a reflective display and transmissive display so that the display system can be switched to the reflective display or transmissive display according to ambient brightness, thereby permitting a clear display while decreasing power consumption even in a dark environment. This type of liquid crystal display device is hereinafter referred to as a “transflective liquid crystal display device,”. An exemplary related art transflective liquid crystal display device includes a reflective film that includes a metal film of aluminum or the like and having light transmission apertures on the inner surface of a lower substrate so as to function as a transflective film. The liquid crystal display device includes the metal film provided on the inner surface of the lower substrate, and thus has the effect of reducing or preventing the influence of parallax due to the thickness of the lower substrate, and reducing or color mixing, particularly, in a structure including a color filter. The liquid crystal-side surface of each of substrates, which constitute a liquid crystal display device, is hereinafter referred to as the “inner surface”, and the opposite surface is hereinafter referred to as the “outer surface”.
FIG. 7 shows an example of a transflective liquid crystal display device including this type of transflective film.
In a liquid crystal display device 100, a liquid crystal layer 103 is sandwiched between a pair of glass substrates 101 and 102, a transflective film 104 having apertures 104a, and a transparent electrode 108 comprising a transparent conductive film of indium tin oxide (hereinafter “ITO”) are laminated on the inner surface of the lower substrate 101, and an alignment film 107 is formed to cover the transparent electrode 108. On the other hand, a transparent electrode 112 including a transparent conductive film of ITO or the like is formed on the inner surface of the upper substrate 102, and an alignment film 113 is formed to cover the transparent electrode 112. Also, two retardation plates 118 and 119 (functioning as a quarter-wave plate 120) and an upper polarizing plate 114 are disposed on the outer surface of the upper substrate 102 in that order from the upper substrate 102, and a quarter-wave plate 115 and a lower polarizing plate 116 are provided on the outer surface of the lower substrate 101 in that order. Furthermore, a back light 117 (illumination device) including a light source 122, a light guide plate 123 and a reflective plate 124 is disposed below the lower polarizing plate 116. Each of the quarter-wave plates 115 and 120 is capable of changing linearly polarized light to substantially circularly polarized light within a certain wavelength region.
The display principle of the transflective liquid crystal display device 100 shown in FIG. 7 is described below with reference to FIG. 8. FIG. 8 shows only components necessary for describing the display principle of the liquid crystal display device shown in FIG. 7.
First, in a dark display, a voltage is applied to the liquid crystal layer 103 (on state) to create a state in which the liquid crystal layer 103 has no phase shift. In a reflective display, light incident on the top of the upper polarizing plate 114 passes through the upper polarizing plate 114 to become linearly polarized light perpendicular to FIG. 8 on the assumption that the transmission axis of the upper polarizing plate 114 is perpendicular to the drawing. Further, the linearly polarized light passes through the quarter-wave plate 120 to become counterclockwise circularly polarized light, which then passes through the liquid crystal layer 103. Then, the circularly polarized light is reflected by the surface of the transflective film 104 provided on the lower substrate 101 to become clockwise circularly polarized light due to inversion of the rotation direction. Furthermore, the circularly polarized light passes through the liquid crystal layer 103, and then passes through the quarter-wave plate 120 to become linearly polarized light parallel to FIG. 8. Since the upper polarizing plate 114 has the transmission axis perpendicular to the FIG. 8, reflected light is not returned to the outside (observation side) due to absorption by the upper polarizing plate 114, thereby causing a dark display.
On the other hand, in the transmissive display, light emitted from the back light 117 passes through the lower polarizing plate 116 to become linearly polarized light parallel to the drawing on the assumption that the transmission axis of the lower polarizing plate 116 is parallel to the drawing. Then, the linearly polarized light passes through the quarter-wave plate 115 to become clockwise circularly polarized light, which then passes through the liquid crystal layer 103. Then, the clockwise circularly polarized light passes through the quarter-wave plate 120 to become linearly polarized light parallel to FIG. 8, which is then absorbed by the upper polarizing plate 114 to cause a dark display in the same manner as the reflective mode.
In a light display with no voltage applied to the liquid crystal layer 103 (off state), a phase shift is set to a quarter wavelength by a birefringence effect of the liquid crystal layer 103. In the reflective display, light is incident on the upper polarizing plate 114 from above, and passes through the upper polarizing plate 114 and the quarter-wave plate 120 to become counterclockwise circularly polarized light, which then passes through the liquid crystal layer 103. Then, the circularly polarized light reaches the surface of the transflective layer 104 to become linearly polarized light parallel to FIG. 8. Furthermore, the linearly polarized light is reflected by the surface of the transflective layer 104, and then passes through the liquid crystal layer 103 to become counterclockwise circularly polarized light, which then passes through the quarter-wave plate 120 to become linearly polarized light perpendicular to FIG. 8. Since the upper polarizing plate 114 has the transmission axis perpendicular to FIG. 8, the reflected light passes through the upper polarizing plate 114 and returns to the outside (observation side), causing a light display.
On the other hand, in the transmissive display, light emitted from the back light 117 passes through the lower polarizing plate 116 and the quarter-wave plate 115 to become clockwise circularly polarized light. Then, the circularly polarized light passes through the liquid crystal layer 103 to become linearly polarized light perpendicular to FIG. 8. The linearly polarized light perpendicular to the drawing passes through the quarter-wave plate 120 to become counterclockwise circularly polarized light. Since the upper polarizing plate 114 has the transmission axis perpendicular to the drawing, only linearly polarized light perpendicular to the drawing of the counterclockwise circularly polarized light passes through the upper polarizing plate 114 to cause a light display.
A related art apparatus is disclosed in Patent Publication No. 3235102.